Introduction

The product described in this invention is a solution composed of an heteropolyacid and a lanthanide salt in hydroalcoholic solvent. The solution can optionally contain an organic or inorganic buffer with a pH between 4-6, or a strong acid or base. The aim of this invention relates also to the use of the solution (and of any reaction product between the components) as negative contrast agent for biologic specimens, a kit containing components or precursors of this solution, and a method to prepare biologic samples for analysis using transmission electron microscopy that employs this solution in at least one phase.

Technical features

The product described in this invention and methods based on the product itself allow overcoming some technical limitations typical of currently employed contrast agents. In particular, the described compound is not toxic or mildly radioactive as in the case of uranyl acetate, which is currently considered the gold standard in electron microscopy. Thus, our product overcomes limitations related to the distribution and disposal of contrast agents. Compared with other commercially available uranium-free contrast agents, our product provides significantly higher contrast level, that reaches, and in some cases overcomes, what shown by uranyl acetate.

Possible Applications

• Safe, economic, and non-toxic replacement of uranyl acetate and other reported contrast agents in all electron microscopy applications.

Advantages

• Negligible toxicity compared with the current “gold standard” in electron microscopy (uranyl acetate);
• No regulatory issues concerning distribution and disposal of the contrast agent;
• Improved performances compared with other commercial alternatives in terms of contrast efficiency.